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Mutluhan Akin,İsmail Akkaya,Müge K. Akin,Ali Özvan,Yusuf Ak 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.8
Jet-grouting as a soil improvement method is extensively preferred in today’s civil engineering practice. High-modulus grout columns constructed by extremely high jetting pressures displace the surrounding soil causing a densification in soil particles. Accordingly, the strength as well as the deformation characteristics of subsurface soils are relatively improved across the compression zone which is under the influence of high jetting pressure. In this study, the modification of soil properties in compression zone after jetgrouting in sandy and clayey soils is investigated by standard penetration tests (SPT) and multi-channel analysis of surface waves (MASW) performed at a couple of construction sites along established jet-grout column rows. The in-situ test results point out significant improvement of the measured parameters compared to initial values. The rate of enhancement in the compression zone is higher in sandy strata than that of clayey deposits. The strengthening of soil due to jetting pressure is validated by finite element analyses as well. Furthermore, very low shear strain values are obtained in clayey soils with respect to the improved characteristics of compression zone representing extremely low shear deformation under foundation.
Analysis of aerodynamic characteristics of 2 MW horizontal axis large wind turbine
Akin Ilhan,Mehmet Bilgili,Besir Sahin 한국풍공학회 2018 Wind and Structures, An International Journal (WAS Vol.27 No.3
In this study, aerodynamic characteristics of a horizontal axis wind turbine (HAWT) were evaluated and discussed in terms of measured data in existing onshore wind farm. Five wind turbines (T1, T2, T3, T4 and T5) were selected, and hub-height wind speed, UD, wind turbine power output, P and turbine rotational speed, Ω data measured from these turbines were used for evaluation. In order to obtain characteristics of axial flow induction factor, a, power coefficient, Cp, thrust force coefficient, CT, thrust force, T and tangential flow induction factor, a', Blade Element Momentum (BEM) theory was used. According to the results obtained, during a year, probability density of turbines at a rotational speed of 16.1 rpm was determined as approximately 45%. Optimum tip speed ratio was calculated to be 7.12 for most efficient wind turbine. Maximum Cp was found to be 30% corresponding to this tip speed ratio.
Akin, Hakan,Tugut, Faik,Mutaf, Burcu,Guney, Umit The Korean Academy of Prosthodonitics 2014 The Journal of Advanced Prosthodontics Vol.6 No.2
PURPOSE. The purpose of this study was to investigate the bonding properties of denture bases to silicone-based soft denture liners immersed in isobutyl methacrylate (iBMA) and 2-hydroxyethyl methacrylate (HEMA) for various lengths of time. MATERIALS AND METHODS. Polymethyl methacrylate (PMMA) test specimens were fabricated (75 mm in length, 12 mm in diameter at the thickest section, and 7 mm at the thinnest section) and then randomly assigned to five groups (n=15); untreated (Group 1), resilient liner immersed in iBMA for 1 minute (Group 2), resilient liner immersed in iBMA for 3 minutes (Group 3), resilient liner immersed in HEMA for 1 minute (Group 4), and resilient liner immersed in HEMA for 3 minutes (Group 5). The resilient liner specimens were processed between 2 PMMA blocks. Bonding strength of the liners to PMMA was compared by tensile test with a universal testing machine at a crosshead speed of 5 mm/min. Data were evaluated by 1-way ANOVA and post hoc Tukey-Kramer multiple comparisons tests (${\alpha}$=0.05). RESULTS. The highest mean value of force was observed in Group 3 specimens. The differences between groups were statistically significant (P<.05), except between Group 1 and Group 4 (P=.063). CONCLUSION. Immersion of silicone-based soft denture liners in iBMA for 3 minutes doubled the tensile bond strength between the silicone soft liner and PMMA denture base materials compared to the control group.
Akin, Omer,Bairamov, Elgiz Korean Mathematical Society 1995 대한수학회지 Vol.32 No.3
This paper is concerned with the problem given below $$ (1.1) i\frac{dx}{du_1(x,\lambda)} + q1(x)u_2(x,\lambda) = \lambdau_1(x,\lambda) 0 \leq x < \infty - i\frac{dx}{du_2(x,\lambda)} + q2(x)u_1(x,\lambda) = \lambdau_2(x,\lambda), $$ $$ (2) u_2(0,\lambda) - hu_1(0,\lambda) = 0 $$ where $\lambda$ is a complex parameter and h is a non-zero complex number.
Relapsed Wilms' tumor with multiple brain metastasis
Akakin, Akin,Yilmaz, Baran,Eksi, Murat Sakir,Yapicier, Ozlem,Kilic, Turker The Korean Pediatric Society 2016 Clinical and Experimental Pediatrics (CEP) Vol.59 No.no.sup1
Wilms' tumor is the most common malignant renal tumor in childhood. The brain metastasis of a Wilms' tumor with anaplastic histopathology is rare. We present the case of an 8-year-old girl with Wilms' tumor, who presented with multiple brain metastases 5 years after her primary diagnosis. The brain masses were diagnosed after a generalized tonic-clonic seizure attack. The big solid mass in the cerebellum was resected, and whole-brain radiotherapy was performed, after which, she succumbed to her disease. In the case of clinical suspicion, cranial surveillance should be included in the routine clinical work-up for Wilms' tumor. Combined aggressive therapy (surgery+radiotherapy+chemotherapy) should be applied whenever possible, for both better survival and palliative aspects.
Akakin, Akin,Yilmaz, Baran,Eksi, Murat Sakir,Kilic, Turker The Korean Neurosurgical Society 2015 Journal of Korean neurosurgical society Vol.57 No.4
Chiari type I malformation is a tonsillar herniation more than 3 mm from the level of foramen magnum, with or without concurrent syringomyelia. Different surgical treatments have been developed for syringomyelia secondary to Chiari's malformations: craniovertebral decompression with or without plugging of the obex, syringo-subarachnoid, syringo-peritoneal, and theco-peritoneal shunt placement. Shunt placement procedures are useful for neurologically symptomatic large-sized syrinx. In this paper, authors define the first successful treatment of a patient with syringomyelia due to Chiari type I malformation using a pre-defined new technique of syringo-subarachnoid-peritoneal shunt with T-tube system.
Effects of Surface Shapes and Geotechnical Conditions on the Ground Motion
Oguz Akin Düzgün,Ahmet Budak 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.5
The influences of surface geometry and local soil properties on ground motion are parametrically studied. The system response is numerically evaluated. In the modelling, finite and infinite elements are applied. Three types of topography (single-faced slopes, canyons and ridges) are taken into account. According to the results, topographic conditions, depth of the rigid bedrock and geotechnical properties have significance in the alteration of ground motion at the irregular soil surface and its surroundings. For all selected surface shapes, the most critical cases occur at top corners especially when the slope gets steeper. These cases are independent on the natural period of structures. The results correspond with those earthquakes where topographical effects are observed and could be seemed to be worthwhile from the perspective of earthquake engineering and seismology.
Merve Akin,Ramazan Bayat,Muhammed Bekmezci,Zeynep Kazel Coguplugil,Fatih Sen,Mehdi Baghayeri,Afsaneh Kaffash,Fatemah Tehranejad‑Javazmi,Iran Sheikhshoaie 한국탄소학회 2023 Carbon Letters Vol.33 No.7
In this research, reduced graphene oxide/polypyrrole (rGO/PPy) particles were synthesized and used to measure the amount of dopamine (DA) electrochemically. The obtained rGO/PPy particle was characterized by Fourier Transform Infrared Spectrophotometer (FTIR), UV–Visible Spectrophotometer (UV–Vis), and X-Ray Diffraction Diffractometry (XRD). To investigate the DA sensor performance, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to acquire electrochemical measurements of the sensor. Current values of 1.65 and 5.9 mA were observed in the CV at 0.2 mM and 1.2 mM concentrations of target molecule, respectively. Under optimized conditions, the linear calibration plots were found to exhibit significant sensitivity in the linear range of 0.2 and 1.2 mM, with a corresponding detection limit of 0.061 μM for DA. The results obtained were similar to the sensor results of DA made using precious metals. This work was a demonstration of the feasibility of high-sensitivity electrochemical analysis with conductive carbon materials without the use of precious metals. It was also observed that the cost-effective rGO/PPy exhibited a very high potential for DA detection.